1. Field of the Invention
The present invention relates to a core retaining apparatus for a wire-cut electro-discharge machine which is capable of effectively and reliably retaining a core cut out of a workpiece by wire-cut electro-discharge machining when the core is removed to a position outside the machining area.
2. Description of the Prior Art
FIG. 4 exemplarily shows a wire-cut electro-discharge machine having a conventional core retaining apparatus which is in a core removing state. In the figure, the reference numeral 6 denotes a workpiece; 7, a core cut out of the workpiece 6; 8, a core holding device which holds the core 7; 9, an arm which supports the core holding device 8; 10, a shaft which is movable up and down while supporting the arm 9 in such a manner that the arm 9 is rotatable about the axis of the shaft 10; 11, a lower dielectric fluid supply nozzle which has a wire electrode (not shown) passed therethrough and which jets out a dielectric fluid (not shown) in the direction of the axis thereof; 12, a support member which supports the lower dielectric fluid supply nozzle 11; 13, an insulating plate to which the support member 12 is secured; and 14, a lower arm which supports the insulating plate 13.
FIG. 5 shows the way in which a core is removed from a workpiece having a back recess. In the figure, the reference numeral 6a denotes a workpiece having a back recess. Since the other reference numerals that are the same as those shown in FIG. 4 denote the same elements or portions, description thereof is omitted.
FIGS. 6A and 6B exemplarily show cutouts which may be made in a workpiece by a machining process, in which the reference numerals 1 to 5 denote cutouts made in the workpiece 6.
The operation will next be explained. To make such cutouts 1 to 5 in series in one workpiece 6, the wire electrode is first passed through a bore provided in the center of the area corresponding to the cutout 1 and machining is carried out with the bore as the starting point. The core 7 that is cut out of the workpiece 6 upon completion of the machining is automatically removed, and subsequently the above-described operation is repeated for the other cutouts 2 to 5, thus executing unmanned continuous machining.
FIG. 4 sows the process of removing the core 7 from the workpiece 6 during the machining process. The core 7 that is cut out of the workpiece 6 upon completion of the machining for the cutout 1 is supported by the lower dielectric fluid supply nozzle 11 that is secured to the support member 12 on the insulating plate 13 attached to the distal end of the lower arm 14 so that the core 7 will not fall into a work tank (not shown). Then, the shaft 10 is rotated so that the core holding device 8 that is provided at the distal end of the arm 9 is moved from a position outside the machining area to a position directly above the core 7. Thereafter, the shaft 10 is lowered so that the core holding device 8 can hold the core 7. Subsequently, the shaft 10 is raised and then rotated to carry the core 7 held by the core holding device 8 to a position outside the machining area. Thereafter, the core holding device 8 releases the core 7.
The conventional core retaining apparatus is arranged such that the core 7 is supported by the upper side of the lower dielectric fluid supply nozzle 11 so that the core 7 will not fall into the work tank upon completion of machining of the cutout 1, for example, when it is removed from the workpiece 6 to a position outside the machining area.
Accordingly, the conventional core retaining apparatus for a wire-cut electro-discharge machine has the following problems:
When the workpiece 6 has a configuration such as that shown in FIG. 5 or the shape of a cutout or the way of using the associated jig or tool is not conformable to the prior art arrangement, the core 7 that is cut out of the workpiece 6 upon completion of a certain machining process cannot effectively be supported by the lower dielectric fluid nozzle 11 and may fall or tilt; in such a case, the core 7 cannot be held by the core holding device 8 and hence cannot automatically be removed.